826 



as having found that Virginia sumac wliich contained 21 per cent of 

 tannin in the leaves in June contained only 15 per cent in August. 

 The author made similar studies on the Bosnian sumac with similar 

 results, as will be evident from the following: 



Tannin in leaves gathered — Pcrcont. 



J line 23 lf<. i'T 



JnlvT 22.97 



Jnly 21 18.89 



August 4 17. 17 



August 18 17. 30 



September 2 16. 83 



The leaves in this case contained the maxin)um quantity of tannin 

 before blooming and at a time when they were generally fully devel- 

 oi)ed. 



In Sicily the leaves are harvested in three peiioils: The lower leaves 

 are gathered l>y the end of May; then, proceeding upwards, the leaves 

 are reniovj-d as fast as they are fully develo]>ed. In this way a product 

 is secured containing as high as L'O ]h'v cent of tannin. Anu'rican sumac 

 is said to reach tlie maxininm eontt-nt of L'7 per cent in .Inly; but as 

 most oft lie uatliering is not done until considerably later, usually before 

 the lea^<'S dry ujt or iVost conn'S, the pnxluct in the niaiket is said to 

 be mn<'h lower than this in tannin. 



(lathering at the time of the maximum tannin content has the 

 further advantage that the i>rodu<t can then be used in making white 

 leather, while the fully ripened or overripe leaves contain a yellowisli 

 brown active coloring matter which unfits them for this purimse. This 

 coloring matter appears in large (piantities in the leaves towards the 

 close of the growing sea.son. It is also rapidly formed in young leaves 

 which arc exposed to the sunlight while in a wilted state, that is 

 before being thonuighly dried, or when they are st<ired in a nu)ist j-ondi- 

 tion. In the first case they also sut!er a lo.ss of tannin: in the last they 

 do not iiidess tlwy mildew, when the tannin diminishes rapidly and the 

 material becomes nuisty. 



I It was i)ointed out by this Department in earlier jmblications that 

 "the cause of the dilVerein-e in itrice in tavor of the Sicilian jiroduct 

 is due to the coloring matter contained in American siunac. which i)re- 

 vents the eini)loyment of the latter in the manufacture of white leather." 

 If it is true, as stated above, that the i)resence of this coloring matter 

 may be avoided by harvesting earlier an<l by i)roper care in drying and 

 stoiing, the cause of the lower ])rice woidd seem to be renu'diable.] 



Contribution to the solution of the nitrogen question, H. 

 ImmendorfiF {Lainhr. Jidirh., JJ 1/>''V), ])}). ;'>/-,?.;.''). — The author pref- 

 aces the report of his own experiments by an histoi ical review of the 

 whcde subject, but more especially that ]»art referring to processes 

 taking idace in soils and in nmnni'es ]>y which combim-d nitrogen 

 is set free and the uucombined nitrogen of the atmosphere is tixcd. 



